Touchballs.glsl

#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif

uniform vec2 resolution;
uniform int pointerCount;
uniform vec3 pointers[10];
uniform float battery;

const float radius = 50.0;
const float stages = 8.0;
const vec3 b = vec3(0.325, 0.0, 0.5);
const vec3 w = vec3(0.325, 1.0, 0.0);

float metaball(vec2 x) {
  x /= battery * 100.0;
  return 1.0 / (dot(x, x) + .00001);
}

void main(void) {
  float p = 0.0;
  for (int n = 0; n < pointerCount; ++n) {
    p += metaball(gl_FragCoord.xy - pointers[n].xy);
  }
  p = ceil(p * radius) / stages;
  gl_FragColor.rgb = w * p + b;
}